This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Despite years of effort, an effective vaccine for HIV remains elusive. Perhaps the greatest obstacle to designing an effective vaccine is a lack of understanding of the immune responses necessary for protection from infection and/or clearance of virus from infected hosts. Furthermore, early cellular and molecular events, particularly in mucosal tissues of HIV infected patients are poorly understood. Further, considerable controversy remains with regard to the earliest virologic and immunologic events in HIV infection, and correlates of immunity to infection or disease progression, which are both critical for developing novel vaccines or immunotherapeutics for prevention or control of infection. The proposed studies will utilize the rhesus macaque model of SIV infection to address the earliest events involved in infection of the intestine, as well as the role of mucosal immunity in control of infection.